28 (198) Society for Experimental Biology and Medicine. 



sium salts to the various nerves failed to produce, in any instance, 

 a phenomenon which could be interpreted as an excitation, but in 

 all cases there was produced, sooner or later, a profound inhibitory 

 effect upon the conductivity of the nerve under experimentation. 

 After application to the sciatic nerve, the conduction of motor and 

 sensory impulses was manifestly inhibited ; a strong stimulus ap- 

 plied below the block caused strong contractions of the muscles 

 of the thigh, but no pain ; when applied above, pain but no contrac- 

 tion was caused. In experiments on the depressor, stimulation on 

 the distal side of the block failed to produce a fall of blood-pres- 

 sure. Applications to the sympathetic blocked the conductivity, 

 so that strong electric stimulations applied to the section of the 

 nerve exposed to the influence of the solution, or distal to that 

 section, failed to cause a constriction of the ear vessels or a dilation 

 of the pupil. 



Instructive results were obtained in the experiments upon the 

 vagi. As is well known stimulation of the central cut end of the 

 vagus produces an unmistakable effect upon respiration, while 

 stimulation of the peripheral cut end causes a standstill of the 

 heart, and a contraction of the esophagus and the cardia. When 

 a section of about 2 cm. to 3 cm. of an intact vagus was exposed 

 for some time to the influence of a solution of a magnesium salt, 

 stimulation above the block affected the respiration but not the 

 heart or the esophagus, and stimulation below affected the function 

 of the last named organs but not that of respiration. 



Applications to the vagus nerves enabled the authors to study 

 the blocking of normal impulses. When applied to one nerve, 

 after the other had been cut, or when applied to both intact nerves, 

 the respirations slowed up perceptibly after a while, as happens 

 after cutting both vagi ; besides, after spontaneous or induced acts 

 of deglutition, no contractions of the esophagus or cardia followed. 



These effects were obtained with hypertonic as well as with 

 isotonic, and even with strongly hypotonic solutions. The weaker 

 the solution the longer it took to establish a complete block ; 10 

 to 30 minutes was about the average time. After a block was 

 established, conductivity could be completely restored by thorough 

 irrigation of the nerve with Ringer solution. When hypotonic 

 solutions of magnesium salts were used, conductivity was often 



